The God of War official website has an interesting easter egg: you'll see links to the first and second God of War prominently displayed, but off to the right-hand side, you'll see a mysterious, burning red Omega sign. Doesn't it look a lot like the promo for the Island of Rhodes?
As of now, the link does not direct you anywhere. However, once the countdown to the Rhodes is done, chances are that will all change. The PS3 God of War will get a number III: the Omega sign is most likely referring to the PSP version which, as you may recall, features an original storyline.